Synchronizer



May 15, 1951 J. D. MCCULLOUGH SYNCHRONIZER Filed Aug. 8, 1945.

BY l

Patented May 15, 1951 UNITED SYN CHRN IZER Jack D. McCuilough, Detroit, Mich., assignor to Chrysler Corporation, Highland Park, Mich., a

corporation of Delaware Application August 8, 1945, Serial No. 609,587

4 Claims. (Cl. 315-29) This invention relates to the production for control purposes of a voltage of constant amplitude in response to a repeated signal and at the same frequency as that of the signal.

More specifically, the invention relates to increasing the usefulness of the ordinary cathode ray oscilloscope, by making it possible to interpret more satisfactorily the patterns formed on a fluorescent screen by the oscilloscope.

When observing and recording oscillographic indications on a cathode ray tube, the operator must continually adjust the frequency of the internal sweep voltage generator, to keep the pattern formed on the screen from drifting to the right or to the left. To be examined in minute detail or to be photographed, the patterns formed on a cathode ray tube must remain stationary in space. Consequently, the frequency of the sweep voltage generator must be in exact synchronism with the observed phenomena.

By methods Well known in the art, it is possible to maintain the proper degree of synchronism only over very small frequency changes, and at the sacrifice of a loss of a portion of the full horizontal voltages.

The invention described herein automatically performs the function of keeping the horizontal .sweep voltage generator in exact synchronism with a given lphenomenon over a very Wide range of frequencies, and with no loss of intelligible information. This means that no matter how the frequency of the phenomenon applied to the first set of deflecting plates of the cathode ray oscilloscope may vary, the sweep voltage applied to the second set of deflecting plates of the cathode ray oscilloscope will be in exact vide improvements in the manner of operation.

of a cathode ray oscilloscope. This Will involve a means for more satisfactorily interpreting patterns formed on a screen by the oscilloscope.

A further object is to provide a control in conjunction with a cathode ray oscilloscope for portions of the invention; and

Fig. 3 shows the application of the invention to an ignition system of an engine.

The invention comprises a system of controls applied to an ordinary gas-triode sawtoothgenerator of a type Well known in the art. However, it is to ybe understood that the method of controls described herein is equally applicable to hard vacuum tube sawtooth generators.

As seen in Fig. 1, there is applied through a path I0, an input voltage that is concurrent With a signal to be observed on one set of deflection plates of a cathode ray oscilloscope, for example, the plates for vertical deiiection. The path I0 branches into paths II and I2, leading, respectively, to a frequency measuring device I4 and acontrol element I5, and to a sawtooth Wave generator I3. The purpose of the input voltage is to initiate a. particular sawtooth Wave on the generator I3 each time the voltage occurs and to operate the frequency measuring device I4. This device produces a Voltage directly proportional to the frequency of the input voltage. The voltage so produced is applied to the control element I5 so as to change its resistance in Va manner necessary to cause the sawtooth generator to produce one sawtooth wave of constant amplitude for each input signal.

In Fig. 2 is shown the sawtooth wave generator I3 including the gas triode tube I6 and its associated condenser Il. In series with the condenser I'I is a control tube I8, a pentode whose apparent plate series resistance may be varied at will by a change of the grid bias voltage applied at line I9. The bias voltage is made to vary with the frequency of the signal observed on the same one set of deflection plates mentioned in the preceding paragraph, which may in the conventional oscilloscope be the plates for vertical deflection-in such a Way as to cause the frequency of oscillation of th-e gas-triode sawtooth wave generator to be substantially synchronous With the frequency of the voltage applied to the said one set of deflection plates. Tubes 20 and 2I, which When combined as shown in Fig. 2, form the frequency measuring device I4, will produce the bias voltage at the line I9 on the control tube IB in direct proportion to the frequency of voltage applied across the vertical deflection plates. Brieiiy, the tubes 20 and 2I produce at junction point 22 one square wave pulse for each input signal. Resistor 23 and condenser 24 form an integrating network, the output voltage of which is proportioned to an average of the voltage applied at the junction point 22.

Consider now the line 25 connected 'to one grid of tube 20. Across this line is to be impressed a signal comprising a recurrent voltage, the frequency of which is equal to that of a signal to be observed. A signal of this frequencyV is impressed across the said one set of deflection plates of a cathode ray oscilloscope, for example, the vertical deflection plates. The purpose ofwimpressing the vsignal of this frequency on the line 25 connected to the various parts described in the preceding paragraph is to obtain another signal of the same frequency to be impressed across the other set of deflection plates of the cathode ray oscilloscope, for example, the horizontal deflection plates. Each signal applied to line 25 is transformed by tubes 2B and 2| into a square wave pulse at junction point 22. Resistor 23 and condensor 24 produce at lead I9 connected to tube I3 a biasvoltage proportional to the frequency of the voltage at junction point 22, which is the same as the frequency of the signal impressed at line 25. Since the apparent plate series resistance of the control tube I8 varies inversely with applied voltage, this resistance varies inversely with the frequency of the signal impressed at line 25.

TheY control tube I8 is so connected with the sawtooth wave generator I3 that the triode tube I6 thereof is connected in series .with the resistance of the control tube I8, which varies inversely with the signal frequency at line 25. Control tube I8 is so adjusted that it causes the tube I6 to be in substantial synchronism with the input signal applied at line 25, because the resistance of tube I8 determines the rate 'of charge of the condenser l1 associated with tube I6, and the resistance of tube |18 varies inversely with signal frequency at line 25. Exact synchronism is assured by biasing grid of tube I6 to cut-off by battery 28 so that this tube can generate a signal only when a signal Vis applied to the grid of tube I through transformer 21 from line 28, in which a signal appears each time a vsignal appears on line 25. The apparatus just described for exact synchronism would by itself cause the amplitude of the signal generated by the sawtooth wave generator I3 to decrease with increase in frequency. Compensation for this is provided in the resistance of control tube I8. This resistance decreases with increase in frequency and therefore brings about a faster charging rate for the condenser I1 with a higher frequency. Thus the amplitude is constant or nearly constant.

The signal of the sawtooth wave generator I3 is received at line 29 and transmitted through a voltage amplifier 30. The increased signal 'goes from the voltage amplifier to horizontal deflection plates 35 and then to a ground 31.

Fig. 3 shows the application of the apparatus of Fig. 2 to an ignition system for an engine, the apparatus of Fig. 2 being designated in Fig. 3 as a horizontal deflection control generator. n A

The line 25 leads to a coil 38 about an arm 39 of an electromagnetic pick-up or current transformer 40, having also a removable arm 4I. Through the pick-up extends a conductor 42 leading from a contact of a distributor 43 for a No. 1 engine cylinder to a spark plug 44. The horizontal deflection plates associated with the output side of the horizontal deflection control generator form part of a cathode ray oscilloscope 45, which also includes vertical deflection plates 48 connected at one side to ground as are the horizontal deflection plates 35. The oscilloscope has the usual electrode gun 41 and the target or screen 48. One of the vertical deflection plates is connected to a conductor 49 leading to a junction point 58 between resistance elements 5I and 52, vconstituting a voltage divider. The voltage divider is grounded at 53. A line 54 leads from the u"Voltage divider to a junction point 55 between a primary winding 56 and a secondary Winding 51 of a transformer. A line 58 leads from the primary Winding 5,8 toa junction point 59, which is grounded as indicated at 68. An energy Asource ,such as a battery @I is connected at one side to the junction po-int 59 and at the othersideto'tlle l'junction point 55t`nroug`h conventionally represented breaker points, shown for illustrative purposes as the ,switch` 62, Iacrossfwhich is connected a capacitor 63. A line 84lea`ds from the secondary winding 5,1'to a rotating arm B5 of -the'distributor 43. The coil 38 is `grounded at 88. Various contacts, shown by the numerals `Ithroug`h 8, inclusive, of the distributor 43are intended to connect to different 'cylinders of ,the complete motor,rwith thepnurmerals adjacent each terminal point beingf indicated inha conventional manner relative to the rotation of the distributor Yarrrl`5. The illustration isV intended'to show one suitable form of firing order, which it may be assumed follows the designations I, 5, 6, 3, 2, and 4, although itis to be understood Vthat this is 'merely given for the purpose of illustration, as is likewise the illustration of the Vassumed siX cylinders, for it is obvious thati'n YautomotiveY engines, the numbermay vary within wide limits, and particularly for aircraft engines the numbers of cylindersand resultantdistributor points are verysubstantialy increased.

There h as been shown onlya singlespark plug element 44 to which energy is supplied by way f the Yconductor 21V connectingY t'o theV 'upper terminal thereof in known manner. lt will be appreciated, however, that otherspark plugs {not shown) connect to eachof the other points v5, B, 3, 2, and I` in substantially like'ma'nner. The energy supplied by way of the breaker points, the transformer andthe distributorto the spark plugs is discharged across the gap provided between points 51 and 5,8, which are also vshown in purely conventional manner. v

In order that the spark discharge may be measured and observed, control vis exerted overthe deflection of a cathode ray beam 69 within Vthe cathode ray oscilloscope 45 in a manner later to be explained. The electro-n gun 41 of the oscilloscope tube 45 is represented in purely schematic form, and is adapted when suitably energized by appropriate operating voltages from sources not shown, to produce. the electron beam 68 Ywhich is directed longitudinally of the tube to strike against the luminescent end wall target or screen 48, Where it produces a luminous trace due to impact.

yIn the path ofthe beam 39 as it moves `from the electron gun 33 to the target or `'screen 4I,

fsuitable deflecting Vmeans are/provided.V These deiiecting means may be either electrostatic or electromagnetic, or a combination of these two forms, but for illustrative purposes, the drawing shows the horizontal deflection as provided by electrostatic means consisting of two deflecting plate electrode members 35, and the vertical deiiection likewise is assumed to be controlled by the electrostatic deflecting plate pair 46. For the purpose of providing horizontal deflection of the electron beam within the tube 45, the horizontal deflection control generator of Fig. 2 has been provided.

rIhe voltage across the primary winding 56 appears each time a spark occurs in any of the spark plugs 11d, and since the vertical deflection plates i5 are connected by the line 49 between the voltage divider 5l, 52 connected between the primary and secondary windings 56 and 51 of the transformer, a vertical deection of the cathode ray beam will be produced by the plates 46 each time a spark occurs at a spark plug.

The horizontal deflection control generator is synchronized through induction produced by current flowing in the line 42 leading to any of the spark plugs e5. and acting through the magnetic pick-up li@ to induce a current in the line 25 leading to the horizontal deflection control generator. The use of' the magnetic pick-up 4G not only effects synchronization of the system but also enables an observer to determine which pattern in the screen 48 is associated with a particular plug. The. pattern of the plug having the conductor l2 with which the magnetic pick-up is associated is at one end of the screen, conventionally, the left end, and the other patterns will follow in order to designate the plugs following in the iiring order after the particular plug. For instance, the magnetic pick-up is associated with the conductor for plug No. 1, and the order of plugs following thereafter is 5--3-2-4. Thus, as indicated, the pattern at the left end of the screen is for plug No. 1, and the other patterns are in order from left to right for plugs Nos. 5-5-3-2-4.

Although the invention has been illustrated as a horizontal deflection control generator for a cathode ray oscilloscope and the oscilloscope is shown to be used for studying the ignition system of an engine, it is to be understood that the invention is not limited in its use to an oscilloscope or to the study of an engine ignition system, but may have many and widely varied uses.

The intention is to limit the invention only within the scope of the appended claims.

I claim:

1. In combination, a first grid-controlled tube having an anode-cathode path, a second gridcontrolled tube having an anode-cathode path, a relatively fixed resistance in common to said tubes in series in the anode-cathode paths for making available a control voltage, a wave generator comprising a condenser having a variable resistance adapted to be controlled by said control voltage, and a third grid-controlled tube connected in parallel with said condenser, means for impressing a recurring signal on the grids of said third and first grid-controlled tubes respectively for discharging said condenser and for causing a voltage pulse to be made available at said resistance in the anode-cathode paths as limited by the value of said resistance and independent of the amplitude of the recurring signal, and means for averaging and applying said pulses to the variable resistance in a manner to vary the value of the latter inversely with the frequency of said pulses and recurring signals ascaos and independently of the amplitude of the curring signals. i

2. In apparatus for observing the spark behavior in a cylindered ignition engine having at least one spark plug, first and second gridcontrolled tubes having anode-cathode paths provided with a common portion, and meansforming a resistance in said common portion for making available a control voltage, a wave generator having a condenser for output adapted to be charged and then discharged to produce a varying output voltage, means for impressing a recurring signal produced as an incident of spark discharge in said spark plug during engine operation, upon said wave generator and on the grid of said irst grid-controlled tube respectively for discharging the condenser at frequency corresponding to the rate of recurrence of spark discharge in said spark plug and for causing a voltage pulse to be made available at said resistance in the anode-cathode paths as limited by the value of said resistance and independent of the amplitude of the recurring spark discharge signal, and means for employing the voltage pulse as control voltage for the wave: generator to vary the charging rate of the con-A denser in proportion to the frequency of the voltage pulse and spark discharge signal and independent of the amplitude of the spark dis-- charge signal.

3. The combination with a cathode-ray oscilloscope having means for producing an electron beam, a rst means for deflecting the electron beam in one of two mutually perpendicular directions, a second means for deflecting the electron beam in the other of the two mutually perpendicular directions, the first deflecting means being energized by a recurring signal and being observed; of a rst grid-controlled tube having an anode-cathode path, a second gridcontrolled tube having an anode cathode path, a relatively fixed resistance in common to said tubes in series in the anode-cathode paths for making available a control voltage, a wave generator comprising a condenser having the output voltage thereof applied to the second deilecting means, and a third grid-controlled tube connected in parallel with said condenser, said condenser having a variable resistance adapted to be controlled by said control voltage for varying the charging rate of the condenser, means for impressing a recurring signal on the grids of said third and rst grid-controlled tubes respectively for discharging said condenser and for causing a voltage pulse to be made available at said resistance in the anode-cathode paths as limited by the value of said resistance and independently of the amplitude of the recurring signal, and means for averaging and applying said pulses to the variable resistance in a manner to vary the value of the latter inversely with the frequency of said pulses and recurring signals and independently of the amplitude of the recurring signals.

4. The combination with a cathode-ray oscilloscope having means for producing an electron beam, a first means for deflecting the electron beam in one of two mutually perpendicular directions, a, second means for deflecting the electron beam in the other of two mutually perpendicular directions, the first deflecting means being energized by a receiving signal and being observed; of iirst and second grid-controlled tubes having anode-cathode paths provided with a common portion, and means forming a resistvable a control voltage, a Wave generator having an dutput condenser adapted to be changed and then; dischair-1ed to produce a varying output volt,- age-applied tothe seco-nd deflecti-ng` means, means for impressing said recurring signal on the wave generatorv and upon the grid of said first gridcontrolled tube: respectively for discharging the condenser to give its output voltage a frequency equal', to that of the signal impressed and for causing a voltage pulse to be made available at; saidi resistance as, limited by the Value of said resistance and independently` of the amplitude ofA` said recurring signal, and meansl for employing the voltage pulse as control voltagev for the wave generator toivary the charging rate of the condenser in proportion tothe frequency of the wiltagev pulse and recurring signal and in dependently of the amplitude of the recurring signal'.

JACK D. MCCULLOUGH.

REFERENCES CITED The following references are of record in the file o this patent:

UNITED STATES PATENTS Number Name Date 11,934,322 Osbon Nov. '7,` 1933 21,266,516 Russell Dec. 16, 1941 2,420,303 De France May 13, 1947 2,448,069, Ames, Jr., et al Aug. 31, 1948 

